Human bodies don’t care whether they're exposed to air pollution indoors or while we’re taking a walk outside. It all has a health impact. For this reason, more scientists and businesses are now focusing on the relationship between outdoor and indoor air pollution.
Indoor Air Pollution Matters (a Lot)
Most people expect air pollution to be something they are more exposed to outdoors than indoors.
However, according to the World Health Organization, indoor smoke from household air pollution presents a serious health risk for as many as 3 billion people (almost half the entire world population!) who cook and heat their homes with biomass, kerosene fuels and coal.
In addition to activities we do indoors that cause harmful air pollution (like candle burning, cooking, and using certain types of cleaning products) it’s also common for poor outdoor air quality to migrate indoors.
In one study, long-range wildfire plumes were found to have elevated average indoor PM2.5 concentrations by up to 4.6 times higher than the outdoors.
The exchange of air pollution also works the other way - as household air pollution can serve as a major source of outdoor air pollution in both urban and rural areas (source).
What is the Indoor-Outdoor Air Pollution Continuum?
Scientists today speak of the indoor-outdoor air pollution continuum to underline the fact that we shouldn’t focus on outdoor or indoor air pollution in isolation.
To understand the true picture of a person’s air pollution exposure, we need to consider the full 24 hour cycle of what an individual has actually breathed in.
This great video from Imperial College London explains the logic behind the indoor-outdoor air pollution continuum very clearly:
Why is it Becoming More Important to Understand Individual Air Pollution Exposure?
We’re Creating More Pollution
Human beings have always been exposed to certain types of ambient air pollution like smoke, dust and fires, but the addition of man-made sources of traffic pollution like industrial emissions has dramatically increased the overall health burden of air pollution exposure.
Today its estimated that 91% of the entire world population live in areas where air quality exceeds safe limits and that 4.2 million deaths each year can be attributed to air pollution exposure.
Seasonal Allergy is Getting Worse
When it comes to respiratory health, pollen exposure is also playing a larger role. Allergic rhinitis (Hayfever) already affects between 10%-30% of the entire world population - and there’s now evidence to suggest this is on the rise - in part, due to climate-change linked rises in allergenic ragweed pollen. Like traditional pollution, pollen can also enter our homes when we open windows or hang our laundry outside.
Unlike other forms of pollution, pollen exposure can only come from the outdoors, again underlining the need to understand the connection between our indoor and outdoor environments.
We’re Inside More
The trappings of modern life mean that people spend on average more than 90% of their time in an enclosed space (see study writeup here). Because we’re indoors so much, prolonged exposure to indoor air pollution even at lower levels can result in significant health impacts over the long-term.
What Can We Expect Going Forward?
As the COVID-19 pandemic continues, even more attention will turn to the importance of integrated indoor air management systems and ventilation technologies designed to prevent the spread of COVID-19 indoors and indoor air contamination in general.
As cited here, global business leaders like Cushman & Wakefield believe
“COVID-19 will cause many companies to acquire extra air filtration solutions in the short term in an effort to promote healthier air”.
The key takeaway here is that COVID-19 highlights the importance of healthy indoor environments even further, helping to push the agenda for round-the-clock personal air pollution exposure monitoring in addition to IAQ regulation.